Precise structures and anti-intrinsic tenase complex activity of three fucosylated glycosaminoglycans and their fragments

Anti-enterovirus 71 activity of native fucosylated chondroitin sulfates and their derivatives

Enterovirus 71 (EV71) is recognized as a major causative agent of hand, foot, and mouth disease (HFMD), posing a significant global public health concern due to its widespread impact and resulting in a major public health issue worldwide. Despite its prevalence, current clinical therapy lacks effective antiviral agents. Fucosylated chondroitin sulfates (FCS) derived from sea cucumber exhibits a range of biological activities including potent antiviral effects. This study provides compelling evidence of the potent antiviral efficacy of FCS against EV71. To further elucidate the impact of structural variations on the anti-EV71 activity, native FCSs with diverse sulfation patterns and a varity of FCS derivatives were prepared and analyzed. Notably, this study presents the detailed structural characterization of FCSs from the sea cucumbers Holothuria scabra Jaege and Holothuria fuscopunctata. Analysis of the structure-activity relationships revealed that molecular weight, sulfated fucose branches, and sulfation pattern were all crucial factors contributing to the potent inhibitory effects of FCS against EV71. Interestingly, molecular weight emerged as the most significant structural determinant of the antiviral potency. These findings suggest the promising potential of utilizing FCS as an innovative EV71 entry inhibitor for the treatment of HFMD.

Purification and Structural Analyses of Sulfated Polysaccharides from Low-Value Sea Cucumber Stichopus naso and Anticoagulant Activities of Its Oligosaccharides

Three polysaccharides (SnNG, SnFS and SnFG) were purified from the body wall of Stichopus naso. The physicochemical properties, including monosaccharide composition, molecular weight, sulfate content, and optical rotation, were analyzed, confirming that SnFS and SnFG are sulfated polysaccharides commonly found in sea cucumbers. The highly regular structure {3)-L-Fuc2S-(α1,}n of SnFS was determined via a detailed NMR analysis of its oxidative degradation product. By employing β-elimination depolymerization of SnFG, tri-, penta-, octa-, hendeca-, tetradeca-, and heptadeca-saccharides were obtained from the low-molecular-weight product. Their well-defined structures confirmed that SnFG possessed the backbone of {D-GalNAc4S6S-β(1,4)-D-GlcA}, and each GlcA residue was branched with Fuc2S4S. SnFS and SnFG are both structurally the simplest version of natural fucan sulfate and fucosylated glycosaminoglycan, facilitating the application of low-value sea cucumbers S. naso. Bioactivity assays showed that SnFG and its derived oligosaccharides exhibited potent anticoagulation and intrinsic factor Xase (iXase) inhibition. Moreover, a comparative analysis with the series of oligosaccharides solely branched with Fuc3S4S showed that in oligosaccharides with lower degrees of polymerization, such as octasaccharides, Fuc2S4S led to a greater increase in APTT prolongation and iXase inhibition. As the degree of polymerization increases, the influence from the sulfation pattern diminishes, until it is overshadowed by the effects of molecular weight.

Structural Characterization and Anticoagulant Activities of a Keratan Sulfate-like Polysaccharide from the Sea Cucumber Holothuria fuscopunctata

A sulfated polysaccharide (AG) was extracted and isolated from the sea cucumber H. fuscopunctata, consisting of GlcNAc, GalNAc, Gal, Fuc and lacking any uronic acid residues. Importantly, several chemical depolymerization methods were used to elucidate the structure of the AG through a bottom-up strategy. A highly sulfated galactose (oAG-1) and two disaccharides labeled with 2,5-anhydro-D-mannose (oAG-2, oAG-3) were obtained from the deaminative depolymerized product along with the structures of the disaccharide derivatives (oAG-4~oAG-6) identified from the free radical depolymerized product, suggesting that the repeating building blocks in a natural AG should comprise the disaccharide β-D-GalS-1,4-D-GlcNAc6S. The possible disaccharide side chains (bAG-1) were obtained with mild acid hydrolysis. Thus, a natural AG may consist of a keratan sulfate-like (KS-like) glycosaminoglycan with diverse modifications, including the sulfation types of the Gal residue and the possible disaccharide branches α-D-GalNAc4S6S-1,2-α/β-L-Fuc3S linked to the KS-like chain. Additionally, the anticoagulant activities of the AG and its depolymerized products (dAG1-9) were evaluated in vitro using normal human plasma. The AG could prolong activated partial thromboplastin time (APTT) in a dose-dependent manner, and the activity potency was positively related to the chain length. The AG and dAG1-dAG3 could prolong thrombin time (TT), while they had little effect on prothrombin time (PT). The results indicate that the AG could inhibit the intrinsic and common coagulation pathways.

Branch distribution pattern and anticoagulant activity of a fucosylated chondroitin sulfate from Phyllophorella kohkutiensis

Fucosylated chondroitin sulfate (FCS) extracted from Phyllophorella kohkutiensis (PkFCS) is composed of d-GalNAc, d-GlcA, l-Fuc and -SO42-. According to the defined structures revealed by NMR spectra of the branches released by mild acid hydrolysis and oligosaccharides generated by β-eliminative depolymerization, the backbone of PkFCS is CS-E, and the branch types attached to C-3 of d-GlcA include l-Fuc2S4S, l-Fuc3S4S, l-Fuc4S, and the disaccharide α-d-GalNAc-1,2-α-l-Fuc3S4S with the ratio of 43:13:22:22. Notably, novel heptasaccharide and hendecasaccharide were identified that are branched with continuous distribution of the disaccharide. The structural sequences of the oligosaccharides indicate that three unique structural motifs are present in the entire PkFCS polymer, including a motif branched with randomly distributed different sulfated l-Fuc units, a motif containing regular l-Fuc2S4S branches and a motif enriched in α-d-GalNAc-1,2-α-l-Fuc3S4S. This is the first report about the distribution pattern of diverse branches in natural FCS. Natural PkFCS exhibited potent anticoagulant activity on APTT prolonging and anti-iXase activity. Regarding the structurally defined oligosaccharides with sulfated fucosyl side chains, octasaccharide (Pk4b) is the minimum fragment responsible for its anticoagulant activity correlated with anti-iXase. However, further glycosyl modification with a non-sulfated d-GalNAc at the C-2 position of l-Fuc3S4S could significantly decrease the anticoagulant and anti-iXase activity.

Comparative Assessment of APTT Reagents for Evaluating Anticoagulant Sensitivity of Fucosylated Glycosaminoglycans (FGs) Derived from Sea Cucumbers

Fucosylated glycosaminoglycans (FGs) derived from sea cucumbers exhibit potent intrinsic Xase (iXase) inhibition, anticoagulation, and antithrombosis. Plasma activated partial thromboplastin time (APTT), a widely used screening test worldwide, is crucial for evaluating anticoagulant efficacy. However, the applicability of these commercially available APTT reagents for assessing anticoagulation of FGs remains unreported. In this study, we investigated the disparity between ellagic acid and colloidal silica APTT reagents in evaluating anticoagulation of dHG-5 and dHLFG-4, two depolymerized FGs, and elucidated the underlying rationale. The results demonstrated that dHG-5 and dHLFG-4 exhibited heightened sensitivity to the ellagic acid APTT reagent both in vitro and in vivo, and did not significantly affect the activation of APTT reagents for plasma. In addition, both ellagic acid and colloidal silica APTT reagents inhibited the anti-iXase of dHG-5 and dHLFG-4, and the inhibition of the ellagic acid APTT reagent was less pronounced compared to the colloidal silica APTT reagent. These findings suggest that the reduced impact of the ellagic acid APTT reagent on the anti-iXase activity of dHG-5 and dHLFG-4 is responsible for the increased sensitivity in plasma APTT analysis. This study offers valuable insights into the characteristics of two APTT reagents applied for assessing the anticoagulant activity of FG-related compounds.

Pharmacology of Heparin and Related Drugs: An Update

Heparin has been used extensively as an antithrombotic and anticoagulant for close to 100 years. This anticoagulant activity is attributed mainly to the pentasaccharide sequence, which potentiates the inhibitory action of antithrombin, a major inhibitor of the coagulation cascade. More recently it has been elucidated that heparin exhibits anti-inflammatory effect via interference of the formation of neutrophil extracellular traps and this may also contribute to heparin's antithrombotic activity. This illustrates that heparin interacts with a broad range of biomolecules, exerting both anticoagulant and nonanticoagulant actions. Since our previous review, there has been an increased interest in these nonanticoagulant effects of heparin, with the beneficial role in patients infected with SARS2-coronavirus a highly topical example. This article provides an update on our previous review with more recent developments and observations made for these novel uses of heparin and an overview of the development status of heparin-based drugs. SIGNIFICANCE STATEMENT: This state-of-the-art review covers recent developments in the use of heparin and heparin-like materials as anticoagulant, now including immunothrombosis observations, and as nonanticoagulant including a role in the treatment of SARS-coronavirus and inflammatory conditions.

Re-understanding of structure and anticoagulation: Fucosylated chondroitin sulfate from sea cucumber Ludwigothurea grisea

Fucosylated chondroitin sulfate (FCS) from sea cucumber Ludwigothurea grisea (FCS_Lg) is the first one that reported to bear the di-fucosyl branches. Here we deciphered it by analyzing the physicochemical properties and its derivatives. Oligosaccharides prepared by selective cleavage of glycosidic linkages presented the mono-fucose and heterodisaccharide branches in FCS_Lg. The disaccharide branch was determined as d-GalNAc_R1-(α1,2)-l-Fuc_R2 rather than the di-fucosyl branch, where R1 was 4-mono-O- or 4,6-di-O-sulfation, and R2 was 3-mono-O- or 3,4-di-O-sulfation, respectively. The diversity of sulfation patterns in branches complicated the structure. These results give us a new understanding of FCS_Lg and provided a reliable method to decipher the FCS with complex branches. Bioanalysis of chemically modified derivatives showed that modulating the molecular mass could enhance the Xase target selectivity. Side chains conferred the Xase complex inhibition by binding to FIXa with a high affinity. Whether monosaccharide and disaccharide branches have differential effects needs to be further explored.

The glycosidic bond cleavage and desulfation investigation of fucosylated glycosaminoglycan during mild acid hydrolysis through structural analysis of the resulting oligosaccharides

Mild acid hydrolysis is a common method to study the chemical structure of fucosylated glycosaminoglycan (FG). It was generally considered that the fucose branches α-L-FucS-(1, of FG could be hydrolyzed selectively in mild acid. This report focused on the selectivity of glycosidic bond cleavage and extensive desulfation characteristics of the backbone during mild acid hydrolysis. The hydrolyzed product of native SvFG (dfSvFG) was prepared by mild acid hydrolysis in 0.1 M H₂SO₄ at 100 °C for 2 h. A series of oligosaccharides were purified by GPC and SAX-HPLC from dfSvFG, then they were analyzed by HPGPC, 1D/2D NMR and ESI-Q-TOF-MS. The precise structure of these oligosaccharides was elucidated to be trisaccharides, tetrasaccharides and pentasaccharides, indicating SvFG branches hydrolyzed basically and its' backbone composed of repeating β-D-GlcA-(1,3)-D-GalNAc and β-D-GalNAc-(1,4)-D-GlcA unit. The prevalent presence of the GlcA residues at the non-reducing terminal of these oligosaccharides, suggesting the glycosidic bond of β-D-GalNAc-(1,4)-D-GlcA was more susceptible to acid than that of β-D-GlcA-(1,3)-D-GalNAc during mild acid hydrolysis. Moreover, the sulfate ester groups in GalNAc_4S6S unit could also be hydrolyzed by acid, and it at position C-4 was more susceptible to hydrolysis than that at C-6. This extensive degradation and desulfation of the backbone should be taken into consideration when mild acid hydrolysis was used in elucidating the exact structure or structure-activity relationship of native FG.

Structural characterization and anticoagulant analysis of the novel branched fucosylated glycosaminoglycan from sea cucumber Holothuria nobilis

Glycosaminoglycan HnFG was extracted from sea cucumber Holothuria nobilis. Its chemical structure was characterized by analyzing the physicochemical properties, oligosaccharides from its mild acid hydrolysates and depolymerized products. The disaccharide d-GalNAc_4S6S-α1,2-l-Fuc_3S-ol found in its mild acid hydrolysates provided a clue for the presence of a unique disaccharide-branch in HnFG. Furthermore, it was confirmed by a series of oligosaccharides from the low-molecular weight HnFG prepared by β-eliminative depolymerization. Combining with the analysis of its peroxide depolymerized products, the precise structure of HnFG was determined: A chondroitin sulfate E (CS-E)-like backbone branched with sulfated monofucoses (~67%) and disaccharides d-GalNAc_S-α1,2-l-Fuc_3S (~33%) at O-3 position of each GlcUA. This is the first report on the novel branches in glycosaminoglycan. Biologically, the native and depolymerized HnFG showed potent activities in prolonging the activated partial thrombin time (APTT) and inhibiting intrinsic coagulation Xase (iXase), whereas the oligosaccharides (degree of polymerization ≤6) had no obvious effects.

Unveiling the Disaccharide-Branched Glycosaminoglycan and Anticoagulant Potential of Its Derivatives

Glycosaminoglycans (GAGs) are conserved polysaccharides composed of linear repeating disaccharides and play crucial roles in multiple biological processes in animal kingdom. However, saccharide-branched GAGs are rarely found, except the fucose-branched one from sea cucumbers. There was conjecture about the presence of disaccharide-branched GAG since 30 years ago, though not yet confirmed. Here, we report a GAG containing galactose-fucose branches from Thelenota ananas. This unique branch was confirmed as d-Gal_4S(6S)-α1,2-l-Fuc_3S by structural elucidation of oligosaccharides prepared from T. ananas GAG. Bioassays indicated that oligomers with a larger degree of polymerization exhibited a potent anticoagulation by targeting the intrinsic tenase. Heptasaccharide was proven as the minimum fragment retaining the anticoagulant potential and showed 92.6% inhibition of venous thrombosis in vivo at sc. of 8 mg/kg with no obvious bleeding risks. These results not only solve a long-standing question about the presence of disaccharide-branched GAG in Holothuroidea, but open up new opportunities to develop safer anticoagulants.

The components and activities analysis of a novel anticoagulant candidate dHG-5

Intrinsic Xase (iXase), the last and rate-limiting enzyme complex in the intrinsic coagulation pathway, may be an ideal target for antithrombotic treatment. A depolymerized fraction of fucosylated glycosaminoglycan from sea cucumber Holothuria fuscopunctata, dHG-5 (Mw 5.2 kDa), showed potent and selective inhibition of iXase (IC₅₀, 14 nM). In this work, the series of oligosaccharides contained in dHG-5 were purified and their precise structures were confirmed by 2D NMR and MS spectra. The relationships between anti-iXase, f.IXa-binding, anticoagulant and antithrombotic activities (y) and molecular weight (x) could be approximately expressed as the power function (y = a × x^b), and these activity potencies of dHG-5 were approximately equivalent to the weighted average sum of that of its oligosaccharides. Given the prominent pharmacological properties, well-defined chemical composition and explicable relationships between dHG-5 and its oligosaccharides in pharmacological behaviors, dHG-5 is expected to be an ideal novel anticoagulant medicine.

(Semi)-Synthetic Fucosylated Chondroitin Sulfate Oligo- and Polysaccharides

Fucosylated chondroitin sulfate (fCS) is a glycosaminoglycan (GAG) polysaccharide with a unique structure, displaying a backbone composed of alternating N-acetyl-d-galactosamine (GalNAc) and d-glucuronic acid (GlcA) units on which l-fucose (Fuc) branches are installed. fCS shows several potential biomedical applications, with the anticoagulant activity standing as the most promising and widely investigated one. Natural fCS polysaccharides extracted from marine organisms (Echinoidea, Holothuroidea) present some advantages over a largely employed antithrombotic drug such as heparin, but some adverse effects as well as a frequently found structural heterogeneity hamper its development as a new drug. To circumvent these drawbacks, several efforts have been made in the last decade to obtain synthetic and semi-synthetic fCS oligosaccharides and low molecular weight polysaccharides. In this Review we have for the first time collected these reports together, dividing them in two topics: (i) total syntheses of fCS oligosaccharides and (ii) semi-synthetic approaches to fCS oligosaccharides and low molecular weight polysaccharides as well as glycoclusters displaying multiple copies of fCS species.

NMR characterization and anticoagulant activity of the oligosaccharides from the fucosylated glycosaminoglycan isolated from Holothuria coluber

A glycosaminoglycan was isolated from the sea cucumber Holothuria coluber (HcFG). A series of oligosaccharide fragments (dp range 3-11) were prepared from its β-eliminative depolymerized product (dHcFG). Extensive NMR characterization of the oligosaccharides indicated the d-GlcA-β1,3-d-GalNAc_4S6S repeating disaccharide backbone was substituted by monosaccharide branches comprising of Fuc_2S4S, Fuc_3S4S and Fuc_4S, linked to O-3 of d-GlcA. For the prevailing Fuc_3S4S at nonreducing end of dHcFG, the β-eliminative depolymerization process of HcFG was compared with those of the FGs from Actinopyga miliaris (AmFG, branched with Fuc_3S4S) and Stichopus variegatus (SvFG, branched with Fuc_2S4S). The result suggested that d-GlcA substituted with Fuc_3S4S was more susceptible to depolymerization than that with Fuc_2S4S. It might be due to the larger steric hindrance effects from Fuc_2S4S on the esterification of GlcA. Biological assays confirmed that the minimum chain length (dp8), regardless of the Fuc branch types, was required for the potent anti-iXase and anticoagulant activities in FG fragments.